As long as you keep your jugs closed and located where they will get sunlight and rainwater (or get hit by the sprinklers), they will grow when they are ready to, which will ususally be sooner than later, due to the "greenhouse" effect of the vessel. I used gallon milk jugs secured from my local Starbucks. They gave them to me by the garbage bag full, for the asking.

The added benefit of WS veggies is that they will be much hardier and hardened off for transplanting.

Having lived (and wintersown) where there is snow, I always count the snow as part of the moisture the helps seeds. I would keep the lids on to make sure the seeds you want is what grows in there. In NY at this time of year, she wants the heat in there, but the lid just vents excess heat! In tx extra heat is bad, in ny, it might help.